General Inquiry on upgrade

Hello all,


This is just a general inquiry, I am a new control systems engineer and would like your insight on control systems upgrade.


What are the top three questions you ask yourself when inspecting a control system for upgrade? for example upgrading all the PLCs



Here is mine:


1. Ask for the control drawings and IO drawings
2. Ask to see the the source code
3. Check the network topology of the current control system


I don't have a basis for my current questions, your insight is greatly appreciated.

I work in process so, the answer may be slightly different for other areas like machinery.



I would ask if the company wants a direct code conversion. If so, then your questions make sense. If however, the goal is upgrade and improvement, then I'd ask for:

- P&ID drawing.

- Interlock list.
- Required instrumentation.
- Control narratives.

- User access specification.

-Communications between any plant DCS/SCADA and other PLCs/systems, notably what physical media and protocol
-I/O or control voltage

ask for a copy of everything they have ! it's what you learn in the documentation that will come back to haunt you .
james

All the above, plus you have to look for the "red flags". One of which is manufacturer or third party modules for which there is no direct replacement in newer PLC equipment.

These can bite you, don't ask how I know!

Upgrades of existing machines or plants cannot be boiled down to 3 top questions.

You need deep insight into how the machine or plant works.
you need to clarify exactly what the upgrade is supposed to achieve. Only a 1-to-1 replacement of the PLC, or also implement new and more modern features, or .... ?
Other than the PLC, shall other parts be upgraded or updated at the same time, i.e. schematics, user manuals, parts catalogues ...
Will safety be affected by the upgrade ?
What is the cost expectation ? (hint, it is always unrealistically low).

When you have have cleared the above, then you can BEGIN to figure out what questions to ask.

JesperMP said:

You need deep insight into how the machine or plant works.
.

Click to expand...

This ^^ x1 million

You can have all the drawings and paperwork you could ever want at your disposal, if you don't understand the process thoroughly, it will never, ever turn out well.

Understanding the current process trumps everything else IMO.

The problem I have run into.... they will not send copies of Electrical Drawings due to copyright infringement.
I have tried to explain that pictures of the drawings will be okay...
Some have gone to sending me an IO list from the drawings.

When you mentioned source code... it sort of raises the hair on my back.
I did an upgrade on a piece of equipment once... When I was done and gone.... The customer just took my material list and source code (Intouch and AB PLC logic) and replicated it to the other 7 pieces of equipment.....

janner_10 said:

This ^^ x1 million

You can have all the drawings and paperwork you could ever want at your disposal, if you don't understand the process thoroughly, it will never, ever turn out well.

Understanding the current process trumps everything else IMO.

Click to expand...

One of the most relevant things I learned while doing plant control was - If you want to know how something REALLY works, try changing it. It is eye-opening, to say the least.